An adjustable housing for apparatus for determining cornea contour

ABSTRACT

An apparatus for determining the contour of the human cornea comprising a substantially opaque target having a plurality of light-transmitting gaps through which light beams can be projected onto the eye of a patient. The pattern of light beams reflected in the eye can then be photographed with the particular configuration providing a basis for determining mathematically the contour of the eye. The target structure comprises a pair of hollow plastic shells provided with an opaque coating. The coating is removed in selected areas to provide the light transmitting gaps. The shells are mounted at one end of an adjustable housing, and a camera and through-the-lens focusing means are located at the opposite end of the housing. The adjusting means comprise double joint ball and socket means which permit the operator to make finite adjustments for accurate alignment while viewing the eye.

Townsley [54] AN ADJUSTABLE HOUSING FOR APPARATUS FOR DETERMINING CORNEACONTOUR Malcolm G. Townsley, Park Ridge, Ill.

The Plastic Contact Lens Chicago, lll.

Filed: Sept. 24, 1970 Appl. No.: 75,131

Related U- APR'FFIQPHPEFFL lnventor:

Assignee: Company,

References Cited UNITED STATES PATENTS 3,463,579 8/1969 lapritz ..35l/38Feb. 1, 1972 [57] ABSTRACT An apparatus for determining the contour ofthe human cornea comprising a substantially opaque target having aplurality of light-transmitting gaps through which light beams can beprojected onto the eye of a patient. The pattern of light beamsreflected in the eye can then be photographed with the particularconfiguration providing a basis for determining mathematically thecontour of the eye. The target structure comprises a pair of hollowplastic shells provided with an opaque coating. The coating is removedin selected areas to provide the light transmitting gaps. The shells aremounted at one end of an adjustable housing, and a camera andthrough-the-lens focusing means are located at the opposite end of thehousing. The adjusting means comprise double joint ball and socket meanswhich permit the operator to make finite adjustments for accuratealignment while viewing the eye.

4 Claims, 15 Drawing Figures PATENTEU EB 1 i 2 SHEET 1 [IF 5 Mm QQ wMHMM M 1m PATENTEU FEB 7 I972 SHEET 2 0F 5 PMENTEU FEB I972 SHEET 3 BF 5PATENTED FEB W72 SHEET b 0F 5 AN ADJUSTABLE HOUSING FOR APPARATUS FORDETERMINING CORNEA CONTOUR This is a division of my copendingapplication Ser. No. 778,965, filed Nov. 26, 1969.

This invention relates to an apparatus designed for determining thecontour of the human cornea. The primary use of the apparatus relates tothe fitting of contact lenses. Thus, the corneas of each individual willvary in contour, and measurements of the contour must be made to providean appropriate design for a contact lens.

Many instruments have previously been designed for purposes of measuringthe shape of the human cornea. These instruments include both visual andphotographic systems for recording the data from which the analysis ofthe corneal shape is to be derived, and several methods have beendescribed for analyzing the information obtained from visual examinationor photographic recording to determine by suitable mathematicalmanipulation of the data, the shape of the cornea.

It is a general object of this invention to provide an improvedapparatus for the preparation of photographs of the human cornea wherebymathematical exercises can be undertaken for purposes of determining thecontour of the cornea.

It is a more specific object of this invention to provide an apparatusof the type described which is capable of providing highly accuratephotographs thereby simplifying mathematical computations and which ischaracterized by a highly efficient and easily handled operatingprocedure.

These and other objects of this invention will appear hereinafter andfor purposes of illustration but not of limitation, the specificembodiments of the invention are shown in the accompanying drawings inwhich:

FIG. I is a side elevational view, partly in section, illustrating theapparatus of the invention;

FIG. 2 is an end elevational view of the apparatus;

FIG. 3 is a vertical sectional view taken about the line 3-3 of FIG. I;

FIG. 4 is a plan view, partly cutaway, of the construction;

FIG. 5 is a detailed, sectional view taken about the line 55 of FIG. 1;

FIG. 6 is a detailed, sectional view taken about the line 6-6 of FIG. 1;

FIG. 7 is a vertical, sectional view taken about the line 77 of FIG. 1;

FIG. 8 is a vertical, sectional view taken about the line 8-8 of FIG. 1;

FIG. 9 is an elevational view of the opposite end of the apparatus;

FIG. 10 is a detailed view of the light pattern developed by the targeton a perfect sphere;

FIG. 11 is a detailed view of the light pattern developed by the targeton an eye having an irregular contour;

FIGS. 12, 13 and 14 are enlarged fragmentary, sectional views ofportions of the target; and,

FIG. 15 is an enlarged fragmentary view illustrating the configurationsof the transparent gap formed in the target.

The apparatus of this invention generally comprises an illustratedtarget designed to develop a light pattern on the eye surface. A camerais positioned in line with the reflected light from the eye forproviding a photographic record of the light pattern.

The improvements of the invention relate to certain structural elementsincluding the target structure. The target is formed from a pair ofhollow plastic shells with one of the shells being conically shaped anddefining an opening at its narrow end portion.

The target shells are covered with an opaque material except in areas,preferably circular, which comprise gaps in the opaque material. A lightsource. is provided behind the target so that a definite light patternis transmitted through thetarget and reflected from the surface of theeye forming a virtual image behind the corneal surface. The constructionis designed so that a known pattern will be formed on a perfectlyspherical element. By means of mathematical calculations, the patterndeveloped on the human eye can be compared with the spherical pattern todetermine the location and extent of variations from a perfect sphere.Suitable mathematical procedures are described in an article by theinventor entitled New Equipment and Methods for Determining the Contourof the Human Cornea appearing in Contacto, Volume II, No. 4, Dec. I967issue, at page 72. In addition to the mathematical discussion, thisarticle discloses background material relative to the subject matter ofthis invention along with many of the features disclosed and claimedherein.

The apparatus of the invention is provided with a throughthe-lensfocusing arrangements so that the operator will have a precise idea ofthe nature of the photograph which will be achieved and can bring theimage into sharp focus and proper centering by observation of theviewing screen. The target and camera are mounted on an adjustablehousing with the controls being such that finite adjustments can be madeto insure accurate alignment. The adjustment of the system isfacilitated through the use of a light tube and mirror combination whichinsures that the line of sight will be in accurate alignment with thecamera lens.

FIGS. 1 through 4 and 9 illustrate a measuring apparatus 10characterized by the features of this invention. The apparatus includesa supporting base 12 which also serves as a housing for some operatingelements to be described.

A head rest construction is provided at one end of the apparatus. Thisconstruction includes a horizontally disposed chin rest 14 and aforehead rest 16. The pads 18 and 20 indicate the specific area forpositioning of the head during a measuring operation.

The head rest arrangement is supported by means of a pair of posts 22extending upwardly from the base 12. One of the posts is provided withan intermediate threaded section 24 having a rotatable adjustingcylinder 26 associated therewith. The adjusting cylinder carries asupporting cylinder 28 with the bar 14 being integrally formed with thissupporting cylinder. The bar 14 defines an opening at its opposite endfor receiving the other post 22. A knurled portion 30 is formed on thecylinder 26, and rotation of this cylinder will provide for raising andlowering of the chin rest bar. The lower ends of the posts 22 aresupported in bores defined by the base 12.

When the head ofa patient is positioned on the rest, adjustments aremade to position the eye 34 centrally of the opening 36 defined by thetarget. This target consists of a pair of shells 38 and 40.

Each of these shells is formed of transparent material. Shell 38 mustreflect a large portion of the light falling on it into the interior ofthe cavity formed by housing 82 and shell 38. This can be accomplishedby coating the interior with an opaque white paint of high reflectanceor with evaporated aluminum as shown at 48. A black enamel coating 50may be applied over the reflective coating 48.

The surfaces of shell 40 must also reflect the light falling on them,but in the case of shell 40, the light enters the body of the plasticmaterial through the edge at 94, so that the polished surface of theplastic shell 40 is, of itself highly reflective for light which iswithin the shell material, and any coating may be dispensed with.Alternatively, both the inner and outer surfaces of shell 40 may becoated with an evaporated coating of aluminum 42 and 44. A black enamel46 may be applied over the coating 44, and a decorative enamel of anydesired color 45, may be applied over the outer surface coating 42.These surfaces define an irregular configuration in order to provideproperly located illuminated target areas. In the case of the shell 38,the sidewall of the shell is stepped at 52. The shell 40 is in the shapeof a cone with wall portions being machined away to provide steps 54 and56. A groove 58 is cut into the step 52, and grooves 60 and 62 areformed in the steps 54 and 56.

An additional groove 64 is formed on the inner face of the angularlydisposed portion 66 adjacent the outer end of the shell 38. Anothergroove 68 is formed in the top wall 70 of the shell 38 adjacent thejuncture with the sidewall. Finally, a pair of grooves 72 and 74 are cutinto the edge 76 at the narrow end of the shell 40. All of the groovesmentioned are provided in the shells prior to the application ofthecoatings.

Once the coatings have been applied, means are provided for removingportions of the coatings in the areas of the several grooves so thatgaps for light transmission may be provided. The shells could, forexample, be placed on a lathe and the coatings machined away.

When the coatings 44, 46, 48 and 50 are initially applied, they willfill the grooves and subsequent machining will leave the coatings in thegrooves. Accordingly, an arrangement such as shown in FIG. will beprovided wherein the groove 64 will be filled with an opaque materialwhile annular gaps 78 will be provided on either side of the groove.This same general relationship will be provided in each instance sincean opaque line will be located in the area of the grooves with openingsfor light transmission located on either side of the line.

A fluorescent light 80 is located within the cylindrical housing portion82 of the construction. Suitable clips 84 are provided to permit easyreplacement of the fluorescent bulb. As best shown in FIG. 1, light fromthe bulb will be directed to the backside of the shell 38 for passagethrough the shell in the areas 86, 88 and 90, these areas being locatedat the positions ofthe grooves 68, 58 and 64, respectively.

The illumination from the fluorescent light will also be passed into theedge 92 of the shell 40, this edge abutting the outer flange 94 of theshell 38. Because of the outer coating 42 and the inner coatings 44 and46, the shell 40 acts as a light pipe. The light will be transmittedthrough the body of the shell and out through the gaps provided in thearea of the steps 54 and 56 and also through the edge 36 of the shell.

The fluorescent light 80 is positioned in surrounding relationshiprelative to an elongated tubular lens holder 96. A threaded member 98 isprovided at the end of the holder, and this threaded member carriesactual lens means.

An eyepiece 100 is provided for the operation. The eyepiece comprises arotatable tubular member provided with screw threads 102 whereby thelens can be adjusted to suit the operator so that the light patternreflected in the eye can be viewed on the split Fresnel screen 104. inaccordance with conventional practice, this arrangement provides ahorizontal offset of the image to insure proper focusing on the screen.The image reflected from the eye can be viewed by the provision of afirst mirror 106 which directs the light onto a second mirror 108 whichin turn directs the light onto the screen 104.

The mirror 108 is provided with an outwardly extending mirror 110 on itsback surface, and a light tube 112 directs light from the lamp 80 to themirror 110. This beam of light is then passed through a hole 107 in thereflecting surface of the mirror 108 and is reflected off the mirror 106through the lens 98 into the eye. The patient then sees a small spotwhich is employed to give a fixation point for the patient duringadjustment and exposure. The lens can be centered on the eye, throughuse ofadjustment means to be described, by means of an autocollimationtechnique. Specifically, the opening 107 in the mirror through which thelight passing from the light tube 112 passes through the mirror 108,will appear as a shadow when viewed against a background of generalillumination provided by the light from the target. The light passingthrough the hole 107 in the mirror is imaged in the cornea by the lens98, and the light is returned to the lens 98 by reflection from thecornea. When the axis ofthe lens 98 is normal to the surface of thecornea at the point where the image is formed, the light is returned tothe lens and the image of the opening 107 in the mirror 106 is returnedto coincide with the opening 107, and the operator can see this brightimage superimposed on the shadow formed on the focusing screen 104 bythe opening 107 as described above, and by bringing the image intocoincidence with the shadow, can insure that the axis of the lens ifnormal to the corneal surface at the point where the image of the hole107 is formed on the corneal surface.

There is provided behind the lens 98 at a distance equal to the focallength of the lens, a cross-wire 99. The light passing from the opening107 in mirror 108 furnishes illumination by which the patient can seethe image of this cross wire formed substantially at an infinitedistance, thereby facilitating his ability to align his visual axis withthe optical axis of the instrument.

The provision of the illuminated dot is also of value in the initialalignment of the instrument during centering of the lens within thetarget. To accomplish this initial alignment, a polished steel ball ofaknown diameter is mounted in the approximate position occupied by apatient's eye. With the ball in place, the lens is adjusted to bring theilluminating spot into coincidence with the pupil" reflection from theball.

The mirror 106 is pivotally mounted on shaft 114, and a rotary solenoid116 is tied to this shaft. This solenoid is connected for energizationwhen the pushbutton 118 is depressed by the operator for purposes ofsecuring a photographic record of the light pattern on the eye. Thesolenoid operation to swing the mirror 106 upwardly whereby lightreflected from the eye will be passed directly to the camera 120. Thiscamera may comprise a modified Polaroid land camera provided with ashutter which will open upon depression of the pushbutton. An electronicflash tube 122 is secured in surrounding relationship relative to thetubular member 96, and this tube is adapted to be flashed by a switch171 which is closed by the mirror 106 when it reaches the upper limit ofits swing. Depression of the pushbutton may also operate to turnoff thelamp during operation of the flash tube.

The tubular housing portion 82 is connected to a double socketcomprising a threaded rod 124, a ball 126 and socket 128, and a secondball 130 and socket 132.

A rear support 137 is connected to the tubular housing 82. This supportcarries rollers 134 which normally ride on the upper surface of the topwall 136 defined by the base 12. A downwardly extending tubular element138 is received in an opening defined by the support 137, and a slot 140is defined by the top wall 136 to permit some freedom of movement forthe member 138.

The rod 124 extends to an adjusting knob 146. The ball 130 is internallythreaded and the rod 124 is externally threaded to enable movement ofthe target structure for the distance permitted by the slot 140. The rod124 is fixed in position relative to the ball 126 by means of clips 147and the target structure moves with the rod due to the connectionbetween the socket 128 and extension 149 ofthe target.

An additional set of rollers 150 is supported on a lower carriage 152.These additional rollers ride against the under surface of the top wall136. A pair of pins 154 are received in bores defined by the lowercarriage 152 and the threaded upper ends of these pins are received bythe support 137. Springs 156 are interposed between the heads of thepins and the seat of the bores to permit movement of the pins 154relative to the wall 136. In the position of the structure shown in FIG.3, the pins are in their lowermost position. When the rod 124 is pivotedby movement of the knob 146, the entire assembly can be pivoted aboutthe location determined by the rollers 150 and 134 and the wall 136 ofbase 12, to bring the opening 34 into the desired relationship with theeye ofthe patient to secure autocollimation as hereinbefore described.Rotation of the knob 146 advances and retracts the entire housing to andfrom the patients eye to achieve proper focusing adjustment and alsodescribed. A packing material 157 is interposed between the ball 130 andthe socket 132 to provide strong frictional engagement so that theassembly can be maintained in this position until the operator againwishes to move the assembly.

Additional pairs of rollers 159 are located between the support 137 andthe lower carriage 152. These rollers are confined in slots 161 definedby the wall 136, and the rollers serve to maintain alignment of thecarriage assembly.

Means are also provided for accurate positioning of the lens holder 96relative to the camera and relative to the target opening 36. Thesemeans include three-clamp screws 160 and three'adjacent setscrews 162located on cars 164 located at the end of the member 96. As shown inFIG. 4, the clamp screw 160 can be rotated to vary the distance betweenthe tubular member and the backwall 166 of the housing 82. Theassociated setscrews are tightened against the cars 164 when the desiredrelationship is achieved. The three-position adjustment permits accurateaxial alignment in the construction.

Appropriate wire leads may extend from within the base 12 through thetubular member 138 which serves as a wire guide. Connections to thesolenoid 116, lamp 80 and electronic flash tube 122 may thus beprovided.

In the operation of the device, the patient places his head in positionwith his chin on the pad 18 and forehead on the pad 20. A switch button170 is provided for turning on the light, and the operator can then lookthrough the eyepiece 100 and see an image of the target pattern on thescreen 104. The spot provided by means of the light tube 112 and mirror110 is then centered relative to the eye by adjusting the position ofthe assembly with the handle 146. Focusing on the screen is alsoachieved by rotation of this handle. When the centering and focusingoperations are completed, the pushbutton 118 is depressed. Any suitableswitch may be actuated by the pushbutton to cutoff current to the lamp80 and to energize the solenoid 116 and the flash tube 122 with timedelay means being provided to delay the last operation. A time delaybetween energization of the solenoid and actuation of the flash also canbe provided by including a switch 171 which will be actuated by themirror 106 to avoid the possibility of the mirror interferring with thepassage oflight to the camera.

FIG. illustrates the preferred light pattern as it would appear on aperfect sphere. It will be noted that a plurality of circular lines areformed, the lines being in pairs due to the provi sion of the groovesbetween the light transmitting gaps. FIG. 11 illustrates an exaggeratedexample of a pattern appearing on a cornea. The bands oflight becomenoncircular thereby illustrating variations from a spherical surface. Bymeasuring the distance from a center point in any direction and bymaking appropriate mathematical calculations, the degree of variationsfrom a sphere can be determined, and the shape of the cornea accuratelycomputed.

In previous practice, patterns such as shown in FIG. 11 have been usedwherein single lines rather than double lines appear. The targetstructure of this invention provides distinct lines due to the presenceof the grooves between adjacent light transmitting gaps. By providingthe narrow opaque area between the gaps, there is a tendency to preventaberrations of the light. Thus, sharper lines are provided on thephotographic reproduction with this arrangement. The use of a pattern ofbright double rings with a dark ring between them has been previouslysuggested.

As shown in FIG. 4, the light patterns include a pair of spots below thecenter and a single spot 172 to the right of center. These spots areprovided due to the presence of holes 174 and 176 defined by the targetshell 38. These small holes are provided so that a person viewing thephotograph can immediately orient the photograph relative to theposition of the eye. Thus, the two dots will always be on the bottomhalf of the eye while the single dot will always be on the right side ofthe eye.

It will be understood that various changes and modifications may be madein the above-described construction which provide the characteristics ofthis invention without departing from the spirit thereof particularly asdefined in the following claims.

I claim:

1. In an apparatus for determining the contour of the human corneawherein an illuminated target is provided for developing a light patternon the eye surface and including a camera for providing a photographicrecord of the pattern, the im provement in means for adjusting theposition of the target structure in order to center the light pattern onthe eye, said adjusting means comprising an externally threaded rod,means extending from said target structure connecting the structure tothe re and a ball and socket secured to a supporting base for the targetstructure, said ball defining a threaded bore receiving the rod meansfor rotating said rod about its own axis for shifting the targetstructure longitudinally relative to said base, and a resilientlymounted rear support means extending between said target structure andsaid base, and further including means allowing for pivotal movement ofsaid target structure about a horizontal axis in response to theapplication of a vertical force component to the rod.

2. An apparatus in accordance with claim 1 wherein said means connectingthe target structure to the rod comprise a second ball and socket, thesecond ball being secured against movement relative to the rod.

3. An apparatus in accordance with claim 1 further including a firstpair of wheels carried by said support and riding on the top surface ofsaid base, a lower carriage means resiliently tied to said rear supportmeans, and a second pair of wheels riding on the underside of said base,said lower carriage and associated wheels yielding relative to said rearsupport means when a vertical component of force is applied.

4. An apparatus in accordance with claim 3 including guide rollerslocated between said lower carriage and said rear support means, saidguide rollers ride in slots formed in said base.

1. In an apparatus for determining the contour of the human corneawherein an illuminated target is provided for developing a light patternon the eye surface and including a camera for providing a photographicrecord of the pattern, the improvement in means for adjusting theposition of the target structure in order to center the light pattern onthe eye, said adjusting means comprising an externally threaded rod,means extending from said target structure connecting the structure tothe rod, and a ball and socket secured to a supporting base for thetarget structure, said ball defining a threaded bore receiving the rodmeans for rotating said rod about its own axis for shifting the targetstructure longitudinally relative to said base, and a resilientlymounted rear support means extending between said target structure andsaid base, and further including means allowing for pivotal movement ofsaid target structure about a horizontal axis in response to theapplication of a vertical force component to the rod.
 2. An apparatus inaccordance with claim 1 wherein said means connecting the targetstructure to the rod comprise a second ball and socket, the second ballbeing secured against movement relative to the rod.
 3. An apparatus inaccordance with claim 1 further including a first pair of wheels carriedby said support and riding on the top surface of said base, a lowercarriage means resiliently tied to said rear support means, and a secondpair of wheels riding on the underside of said base, said lower carriageand associated wheels yielding relative to said rear support means whena vertical component of force is applied.
 4. An apparatus in accordancewith claim 3 including guide rollers located between said lower carriageand said rear support means, said guide rollers ride in slots formed insaid base.